Optical Contact Research Articles

Tissue-probe contact assessment during robotic surgery using single-fiber reflectance spectroscopy

The introduction of robotic surgery has improved minimally invasive surgery, and now robotic surgery is used in several areas of surgical oncology. Several optical techniques can be used to discriminate cancer from healthy tissue based on their optical properties. These technologies can also be employed with a small fiber-optic probe during minimally invasive surgery; however, for acquiring reliable measurements, some optical techniques require the fiber-optic probe to be in direct contact with the tissue. The lack of tactile feedback in robotic surgery makes assessing tissue-probe contact suitable for optical contact measurements challenging for the surgeon. In this study, we investigated the use of single fiber reflectance (SFR) to determine tissue-probe contact adequately. A machine learning-based algorithm was developed to classify if direct tissue-probe contact was present during the measurement in an ex-vivo tissue setup. Using this classification algorithm, an average accuracy of 93.9% was achieved for assessing probe-tissue contact, suggesting that this technique can be utilized to assess tissue-probe contact in an in vivo clinical setting.

Osteoblast Response to Widely Ranged Texturing Conditions Obtained through High Power Laser Beams on Ti Surfaces.

Titanium and titanium alloys are the prevailing dental implant materials owing to their favorable mechanical properties and biocompatibility, but how roughness dictates the biological response is still a matter of debate. In this study, laser texturing was used to generate eight paradigmatic roughened surfaces, with the aim of studying the early biological response elicited on MC3T3-E1 pre-osteoblasts. Prior to cell tests, the samples underwent SEM analysis, optical profilometry, protein adsorption assay, and optical contact angle measurement with water and diiodomethane to determine surface free energy. While all the specimens proved to be biocompatible, supporting similar cell viability at 1, 2, and 3 days, surface roughness could impact significantly on cell adhesion. Factorial analysis and linear regression showed, in a robust and unprecedented way, that an isotropic distribution of deep and closely spaced valleys provides the best condition for cell adhesion, to which both protein adsorption and surface free energy were highly correlated. Overall, here the authors provide, for the first time, a thorough investigation of the relationship between roughness parameters and osteoblast adhesion that may be applied to design and produce new tailored interfaces for implant materials.

Early Biological Response to Poly(ε-Caprolactone)/Alumina-Toughened Zirconia Composites Obtained by 3D Printing for Peri-Implant Application.

The improvement of the mucosal sealing around the implant represents a challenge, one that prompted research into novel materials. To this purpose, a printable poly(ε-caprolactone) (PCL)-based composite loaded with alumina-toughened zirconia (ATZ) at increasing rates of 10, 20, and 40 wt.% was prepared, using a solvent casting method with chloroform. Disks were produced by 3D printing; surface roughness, free energy and optical contact angle were measured. Oral fibroblasts (PF) and epithelial cell (SG) tests were utilized to determine the biocompatibility of the materials through cell viability assay and adhesion and spreading evaluations. The highest level of ATZ resulted in an increase in the average roughness (Sa), while the maximum height (Sz) was higher for all composites than that of the unmixed PCL, regardless of their ATZ content. Surface free energy was significantly lower on PCL/ATZ 80/20 and PCL/ATZ 60/40, compared to PCL and PCL/ATZ 90/10. The contact angle was inversely related to the quantity of ATZ in the material. PF grew without variations among the different specimens at 1 and 3 days. After 7 days, PF grew significantly less on PCL/ATZ 60/40 and PCL/ATZ 80/20 compared to unmixed PCL and PCL 90/10. Conversely, ATZ affected and improved the growth of SG. By increasing the filler amount, PF cell adhesion and spreading augmented, while PCL/ATZ 80/20 was the best for SG adhesion. Overall, PCL/ATZ 80/20 emerged as the best composite for both cell types; hence, it is a promising candidate for the manufacture of custom made transmucosal dental implant components.

Improved Femtosecond Laser Welding of Nonoptical Contact Glass by Pressure and a Water Intermediate Layer.

Ultrafast laser welding has emerged as a significant technology for the joining of transparent materials and has been extensively researched for the welding of glass materials in recent years. However, achieving a robust connection requires optical contact between the samples during laser processing, which complicates the welding process and increases its cost. To achieve high-strength welding of glass samples without optical contact, the samples are typically pressed together to minimize the gap, allowing the molten materials to completely fill it. In this study, two approaches are employed to facilitate high-strength welding of silica glasses: femtosecond (fs) laser welding with the assistance of pressure using a fixture and femtosecond laser welding aided by a water intermediate layer. The welding quality achieved by both methods is thoroughly examined and compared. The findings reveal that femtosecond laser welding with water assistance outperforms other methods in terms of welding uniformity and quality. Furthermore, the principle behind achieving high-quality welding is discussed to elucidate the success of this method.

Realization of Joints of Aluminosilicate Glass and 6061 Aluminum Alloy via Picosecond Laser Welding without Optical Contact.

To achieve laser direct welding of glass and metal without optical contact is hard, owing to the large difference in thermal expansion and thermal conductivity between glass and metal and an insignificant melting area. In this study, the high-power picosecond pulsed laser was selected to successfully weld the aluminosilicate glass/6061 aluminum alloy with a gap of 35 ± 5 μm between glass and metal. The results show that the molten glass and metal diffuse and mix at the interface. No defects such as microcracks or holes are observed in the diffusion mixing zone. Due to the relatively large gap, the glass collapsed after melting and caulking, resulting in an approximately arc-shaped microcrack between modified glass and unmodified glass or weakly modified glass. The shape of the glass modification zone and thermal accumulation are influenced by the single-pulse energy and linear energy density of the picosecond laser during welding, resulting in variations in the number and size of defects and the shape of the glass modification zone. By reasonably tuning the two factors, the shear strength of the joint reaches 15.98 MPa. The diffusion and mixing at the interface and the mechanical interlocking effect of the glass modification zone are the main reasons for achieving a high shear strength of the joint. This study will provide reference and new ideas for the laser transmission welding of glass and metal in the non-optical contact conditions.

A Field Research on the Problems Experienced by Opticians and Optical Stores

The optician profession forms an important bridge between ophthalmologists and patients in the treatment of eye diseases and refractive errors. Optical glasses, frames, contact lenses and other devices are provided and applied by opticians in accordance with prescriptions written by ophthalmologists. However, the optician profession and institutions in Turkey face various problems. This research aims to identify and analyze issues such as education and qualification problems, regulatory difficulties, economic difficulties and adaptation to technological innovations experienced by the optician profession and institutions in Turkey. By evaluating the opinions and expectations of different stakeholders, solution suggestions and strategies will be developed to make the profession more efficient and effective. Thus, it is aimed that the results of the study will contribute to the future development of the optician profession and its institutions.

Thermal and Mechanical Properties of Bio‐Based Polyamide 56/6 Filled with Talc

AbstractPolyamide composites with varying filler concentrations are prepared using the hot melt extrusion method, employing polyamide 56/6 (PA56/6) and modified talc as fillers. Initially, the thermal characteristics of PA56/6 composites (PA56/6‐talc) are examined through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), encompassing parameters such as melting temperature, crystallinity, and decomposition temperature. The hydrophilicity and barrier properties of PA56/6‐talc are assessed using an optical contact angle meter, a water vapor transmission rate tester, and an oxygen transmission rate tester. Furthermore, the mechanical properties of PA56/6‐talc are also scrutinized. The results indicate that PA56/6 exhibits superior hydrophobic, barrier, and mechanical properties, thereby demonstrating its immense potential in garment fabrics and packaging materials.

Precise refractive index measurement of fused silica optics

Abstract We have developed an experimental platform that non-destructively and precisely measures the Refractive Index (RI) and dispersion of ultra-polished fused silica optics. Using Total Internal Reflection Digital Holographic Microscopy (TIRDHM), we exploit the phase change of reflected light in Total Internal Reflection (TIR) mode. This phase change depends on the incident angle at the TIR interface and the refractive indices of the involved media. We have optimized a combination of higher TIR phase sensitivity, considerable penetration depth, and minimized phase measurement inaccuracies through simulations to design our experiment. Key features include a custom-made precision Right-Angle Prism (RAP) of Astrositall material, a seamless interface with fused silica optics on TIR interface through optical contact, and single-shot measurement. We have demonstrated the accuracy of measuring fused silica optics through proof of concept and experimental results. Our measurements on two different samples show accuracy better than ±3 × 10−4 compared to those obtained using a commercially available critical angle Refractometer (Metricon). Importantly, the setup offers the advantage of spatially mapping the refractive index, unlike point measurements by available Refractometers.

Transparent Recombination Layers Design and Rational Characterizations for Efficient Two-Terminal Perovskite-Based Tandem Solar Cells.

Two-terminal (2T) perovskite-based tandem solar cells (TSCs) arouse burgeoning interest in breaking the Shockley-Queisser (S-Q) limit of single-junction solar cells by combining two subcells with different bandgaps. However, the highest certified efficiency of 2T perovskite-based TSCs (33.9%) lags behind the theoretical limit (42-43%). A vital challenge limiting the development of 2T perovskite-based TSCs is the transparent recombination layers/interconnecting layers (RLs) design between two subcells. To improve the performance of 2T perovskite-based TSCs, RLs simultaneously fulfill the optical loss, contact resistance, carrier mobility, stress management, and conformal coverage requirements. In this review, the definition, functions, and requirements of RLs in 2T perovskite-based TSCs are presented. The insightful characterization methods applicable to RLs, which are inspiring for further research on the RLs both in 2T perovskite-based two-junction and multi-junction TSCs, are also highlighted. Finally, the key factors that currently limit the performance enhancement of RLs and the future directions that should be continuously focused on are summarized.

Stabilization of oil‐in‐water emulsion gels by pH‐induced electrostatic interactions between soybean protein isolate microgel particles and xanthan gum

AbstractIn this paper, a colloidal dispersion at different pH containing soybean protein isolate (SPI) microgel particles and xanthan gum (XG) was used as the aqueous phase to prepare O/W emulsion gels with soybean oil. Properties of SPI microgel particles were analyzed by particle size, Zeta‐potential, secondary structure, optical contact angle, dynamic interface tension, and SEM testing, respectively. Results showed that pH impact microgels particle size and Zeta‐potential and their emulsification properties. It turned out that only at pH 3, 6, 7, and 8 can construct emulsions successfully. Based on a comparison of microstructure and macroscopic properties, it was found that at pH 3, proteins and polysaccharides were oppositely charged, electrostatic attraction between them reduced proteins located at the interface, and was more likely to form larger droplets, resulting in a bimodal droplet distribution and larger sizes. Conversely, at the pH of 6, 7, and 8, respectively, emulsions exhibited a uniform droplet distribution and more solid‐like rheological properties due to the powerful electrostatic repulsion between SPI and XG. Also, emulsion gels co‐stabilized with proteins and polysaccharides under electrostatic repulsion conditions showed an ideal recovery ability. Overall, this work would be beneficial to the use of emulsion gels in fat substitute systems.

Preparation and Corrosion Resistance of OMMT/EP Composite Coatings in Sulfur-Containing Sodium Aluminate Solution

Organic montmorillonite (OMMT) was prepared from Na-montmorillonite (MMT) by Hexadecylamine (HDA) modification. The composite material has good smoothness, acidity, and salt resistance. OMMT was characterized using small-angle X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and a video optical contact angle measuring instrument. The results showed that the layer spacing was enlarged from 1.44 nm to 2.87 nm after the modification, and the hydrophobicity performance was greatly improved. The organic modification of MMT was successful. The surface morphology, roughness, and anticorrosion properties of the organic montmorillonite/epoxy (OMMT/EP) composite coating were investigated and compared with those of the epoxy (EP) coating. The OMMT/EP composite coating had a flatter surface than the EP coating. The roughness was reduced from 65.5 nm to 10.3 nm. The electrochemical impedance spectroscopy showed that the composite coating’s thickness positively affected its anticorrosion performance, the corrosion current density (Icorr) decreased with the increase in thickness, and its maximum impedance was much larger than that of EP coating. The protection efficiency of the OMMT/EP composite coating was 77.90%, which is a significant improvement over the EP’s 31.27%. In addition, the corrosion resistance of the composite coating gradually decreased with increasing immersion time, but the change was insignificant.

Structural Micromodification of Diamond by Femtosecond Laser Pulses Through Optical Contact with a Nonlinear Highly Refractive Immersion Medium

Structural Micromodification of Diamond by Femtosecond Laser Pulses Through Optical Contact with a Nonlinear Highly Refractive Immersion Medium

Using clinical optical coherence tomography to characterise contact lens edge shape and base curve radius

ABSTRACT Clinical relevance Clinical optical coherence tomography devices are widely used in optometry and ophthalmology and may be used to measure contact lens base curvature radius and visualise contact lens edge shape. Background Knowledge of contact lens geometry facilitates fitting, while optical coherence tomography provides a powerful means of measuring geometrical form. This study evaluates the performance of a clinical optical coherence tomography device (3D OCT-1000) in characterising contact lens edge shape and measuring the back optic zone radius of rigid gas-permeable contact lenses in vitro. Methods First, an opto-mechanical optical coherence tomography contact lens adaptor was designed and 3D-printed to facilitate a contact lens being imaged using a commercial optical coherence tomography device. Second, several image-processing algorithms and a simple calibration method were developed to measure the back optic zone radius in optical coherence tomography B-scans. Finally, based on the findings of two experiments, B-scan performance was evaluated in terms of 1) capacity to differentiate between contact lens edge geometries, and 2) capacity to obtain accurate and repeatable back optic zone radius measurements. Statistical and graphical analyses were performed to characterise reliability and reproducibility. Results The 3D OCT-1000 and adaptor combination was capable of acquiring images of sufficient quality to discriminate between soft and rigid contact lens edge geometries. Additionally, statistical analysis of the rigid contact lens measurements demonstrated satisfactory back optic zone radius measurement accuracy and reproducibility. Conclusion This study demonstrates that a 3D OCT-1000 fitted with an opto-mechanical adaptor combination can be used to assess contact lens edges in vitro and that this clinical optical coherence tomography device, combined with image processing and linear calibration of the B-scans, is capable of obtaining back optic zone radius measurements of rigid gas-permeable contact lenses that are close to the ISO 18,369-2:2018 manufacturing tolerance range (±0.05 mm).

Improvement of hybrid liquid membrane performance in removal of cadmium from wastewater using GO filled-polyethersulfone membrane

ABSTRACT The removal of cadmium as a heavy metal using a hybrid liquid membrane consisting of an organic liquid phase membrane surrounded by two supporting polymeric membranes was investigated in the present study. The supporting membranes were mixed matrix membranes consisting of graphene oxide (GO) incorporated in polyethersulfone (PES) matrix. The organic liquid membrane was trioctylamine (TOA) as the carrier dissolved in kerosene as the solvent. The synthesized GO and the fabricated supported membrane were characterized using X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), atomic force microscopy (AFM), and optical contact angle (OCA). The effects of GO content in the supporting membrane, carrier concentration, pHs of feed and stripping phases, feed concentration, temperature, mixing intensity, acid type, and organic phase thickness on cadmium removal were studied. The GO-containing PES supporting membrane showed higher cadmium removal efficiency than that of the unfilled PES membrane in the process owing to the higher hydrophilicity and pore size of the fabricated membrane as well as the membrane’s surface charge that promotes the mass transfer at the feed/liquid phase interface. The removal efficiency of up to 90% could be attained at mixing intensity of 500 ppm, temperature of 60°C, GO content of 0.2%, carrier concentration of 0.1 M, feed phase pH of 1.8, and a stripping phase pH of 13.

The evolution process of fractures and their modification effects on the liquid–solid interface during liquid nitrogen cyclic freeze–thaw of coal and shale

Liquid nitrogen cyclic freezing-thawing fracturing (LNCFT) is an innovative method for the waterless fracturing of coal and rock, harnessing the effects of low temperature, phase change, and expansion. However, the mechanisms behind micro-fracture propagation, evolution, and surface modification during LNCFT remain elusive. This study concentrates on anthracite coal and roof shale in the Jiaozuo mining area. It conducts LNCFT experiments under various saturated water conditions and employs a stereoscopic fluorescence microscope and an optical contact angle measuring instrument for observations, analyzing the surface modification effects resulting from the propagation and evolution of fractures on solid surfaces. The study unveils the following findings: (1) LNCFT effectively creates a network of micro-fractures. The quantity and length of fractures significantly increase with the number of fracturing cycles, and the effect is more pronounced with higher water content, especially in coal compared to shale. Fracture evolution falls into three categories: extension, intersecting, and newly formed independent fractures, with the scale of extension and intersecting of the original fractures determining the modification effect. (2) The LNCFT process exhibits distinct stages and selectivity. The strength of early-stage modifications (before eight cycles) directly influences the overall modification effect. (3) Throughout the LNCFT process, the solid–liquid surface contact angle first increases and then decreases with the number of fracturing cycles. This pattern can be analyzed using the Wenzel model. Liquid nitrogen fracturing increases the surface roughness of coal and shale, leading to a transition from hydrophobicity to hydrophilicity on their surfaces. The research findings of this paper provide theoretical guidance for the modification of low-permeability reservoirs.

Surface treatments of the zirconia-reinforced lithium disilicate ceramic in the adhesion to the resin cement.

This study verified the effect of surface treatments of the zirconia-reinforced lithium disilicate ceramic bonded to resin cement. Ceramic blocks were divided according to treatments (n=10): FA+SRX (Fluoric acid + silane RX), FA+MDP (Fluoric acid + MDP), FA+SCF+MDP (Fluoric acid + silane CF + MDP), FA+MEP (Fluoric acid + MEP), and MEP (Self-etch primer). Resin cement cylinders were made in the ceramic blocks, photoactivated with 1,200 mW/cm² for 40s, stored in water at 37°C for 24h, and evaluated by the microshear strength test, optical failure descriptive analysis (%), surface characterization (SEM) and contact angle (Goniometer). Other samples were submitted to 10,000 thermocycles between 5°C and 55°C. Bond strength data were submitted to two-way ANOVA and Tukey's test. Contact angle to one-way ANOVA and Games-Howell's test (5%). At 24h, MEP showed higher bond strength, and FA+SRX the lower. FA+MDP and FA+SCF+MDP showed similar values and FA+MEP was intermediate. After thermocycling, FA+SCF+MDP, FA+MEP, and MEP showed higher values, and FA+SRX the lower while FA+MDP was intermediate. When the periods were compared, FA+MDP, FA+SCF+MDP, FA+MEP, and MEP showed higher values for 24h while FA+SRX was similar. SEM showed retentive surface and crystal exposure when treated with FA+SCF+MDP. The less retentive surface was obtained with MEP, and the other treatments promoted intermediate irregularities. In conclusion, surface treatment and thermocycling promoted different values of adhesive strength and contact angle in a zirconia-reinforced lithium silicate ceramic. Failures were predominantly adhesive, and the ceramic surface was characterized by different levels of roughness and selective exposure of crystals.

Prevention aid in qualitative analysis of dermatoglyphic patterns in relation to type 2 diabetes mellitus: a pilot study.

The significant differences in the fingerprint pattern frequencies in type 2 diabetes mellitus (T2DM) patients and controls could be a possible way to identify patients with a risk of developing T2DM. The results could be used in the earlier diagnosis and treatment. The study was undertaken to find out the reliability of fingerprint patterns as a possible predictive tool for T2DM diagnosis. A total of 1,260 fingerprints were acquired using the optical contact sensor DactyScan 26i. The results of the qualitative analysis of the fingerprint pattern frequencies have been compared between T2DM patients and controls and also between the fingers to each other. We have detected the frequency of patterns: plain arch (Ap) and tented arch (At), radial loop (Lr), ulnar loop (Lu), double loop (Ld), spiral whorl (W), and plain whorl (concentric) (Wp). Statistical analysis was performed using Pearson's chi-square by Statistica ver. 12. We found statistically significant differences (p < 0.05) in the frequency of individual dermatoglyphic patterns among patients with diabetes and healthy controls as follows: in the left thumb (L1) in a radial loop, double loop and spiral whorl pattern; in the left middle finger (L3) in a tented arch and radial loop; in the right ring finger (R4) in a tented arch, spiral and plain whorl; and in the right little finger (R5) in a tented arch and spiral whorl. Fingerprint pattern frequencies might be used as another screening tool and indicator in T2DM prevention. Qualitative analysis of fingerprint patterns could be useful regarding the additional prevention diagnostics of T2DM in the population.

Inert-Atmosphere Microfabrication Technology for 2D Materials and Heterostructures.

Most 2D materials are unstable under ambient conditions. Assembly of van der Waals heterostructures in the inert atmosphere of the glove box with ex situ lithography partially solves the problem of device fabrication out of unstable materials. In our paper, we demonstrate an approach to the next-generation inert-atmosphere (nitrogen, <20 ppm oxygen content) fabrication setup, including optical contact mask lithography with a 2 μm resolution, metal evaporation, lift-off and placement of the sample to the cryostat for electric measurements in the same inert atmosphere environment. We consider basic construction principles, budget considerations, and showcase the fabrication and subsequent degradation of black-phosphorous-based structures within weeks. The proposed solutions are surprisingly compact and inexpensive, making them feasible for implementation in numerous 2D materials laboratories.

Enhanced Performance of Solar‐Blind UV Photodetector Based on β‐Ga2O3 Nanowires Grown by a Magnetron Sputtering

The development of simple and highly controllable fabrication methods for the β‐Ga2O3, especially for the nanowire structure, has been a challenge. The slanted Ga2O3 nanowires are favorable for increasing the optical contact area and improving photon flux through nanoparticle scattering, leading to an increase in the photogenerated carrier yield. Herein, obliquely oriented and uniformly distributed β‐Ga2O3 nanowires are fabricated on Si substrates by a radio frequency magnetron sputtering using the strategy of Au nanoparticles as an intermediate catalyst. By depositing Ti and Au electrodes, the metal–semiconductor–metal Ga2O3‐based photodetectors are fabricated with a simple structure. Remarkably, the photodetector based on the β‐Ga2O3 nanowires outperforms the one based on the β‐Ga2O3 film, demonstrating higher responsivity and an exceptional photocurrent‐to‐dark current ratio (Iphoto/Idark) of 1.43 × 104 @5 V. This work presents a promising approach to enhance the utilization of incident light and maximize the generation of photoinduced carriers in the Ga2O3‐based photodetectors.

INFLUENCE OF ASPECT RATIO OF TEMPO-OXIDIZED CELLULOSE NANOFIBERS (TOCNs) FROM WOOD PULP ON POLYMERIC MEMBRANE PROPERTIES

The incorporation of TEMPO-oxidized cellulose nanofibers (TOCNs) derived from wood pulp resulted in an improvement in the characteristics of polymeric membranes made up of poly (methyl vinyl ether maleic acid)/PMVEMA and poly (ethylene glycol)/PEG. The membranes were constructed, and TOCNs were included in the formulation at a rate of 5 wt%. TOCNs were categorized as either short or long, depending on the aspect ratio measurement. According to the findings of the research, the various lengths of TOCNs resulted in variances in the optical transmittance properties, contact angles, and whiteness level of the membranes, in addition to a little variation in the tensile and thermal properties of the material. When compared to short TOCNs, long TOCNs offer somewhat improved performance in terms of optical transmittance, whiteness level, tensile characteristics, and thermal stability. The results of this study reveal the significance of the morphology of nanocellulose in determining the properties of the composite that includes it. Thus, the characteristics of the target membrane were greatly influenced by nanocellulose morphology.